Opportunistic p-persistent CSMA in wireless networks

In this paper, Opportunistic p-persistent Carrier Sense Multiple Access (OpCSMA) is proposed to incorporate multiuser diversity into p-persistent CSMA. In the OpCSMA, each mobile terminal (MT) is assumed to have the knowledge of its channel state information (CSI). At each idle time slot, an MT sends a packet if the corresponding channel gain is above the threshold, which is determined such that the probability of accessing the medium is maintained to be p for any idle slots. Using the infinite user model, it is proved that the OpCSMA provides significant increase in the expected capacity compared to p-persistent CSMA. In addition, the expected capacity of the OpCSMA is shown to be proportional to ln G at low SNR where G is the offered load. Simulation results corroborate the above findings in slow fading channels.